Energetic cost of brain functional connectivity Tomasi, Dardo; Wang, Gene-Jack; Volkow, Nora D.
Proceedings of the National Academy of Sciences,
08/2013, Volume:
110, Issue:
33
Journal Article
Peer reviewed
Open access
The brain's functional connectivity is complex, has high energetic cost, and requires efficient use of glucose, the brain's main energy source. It has been proposed that regions with a high degree of ...functional connectivity are energy efficient and can minimize consumption of glucose. However, the relationship between functional connectivity and energy consumption in the brain is poorly understood. To address this neglect, here we propose a simple model for the energy demands of brain functional connectivity, which we tested with positron emission tomography and MRI in 54 healthy volunteers at rest. Higher glucose metabolism was associated with proportionally larger MRI signal amplitudes, and a higher degree of connectivity was associated with nonlinear increases in metabolism, supporting our hypothesis for the energy efficiency of the connectivity hubs. Basal metabolism (in the absence of connectivity) accounted for 30% of brain glucose utilization, which suggests that the spontaneous brain activity accounts for 70% of the energy consumed by the brain. The energy efficiency of the connectivity hubs was higher for ventral precuneus, cerebellum, and subcortical hubs than for cortical hubs. The higher energy demands of brain communication that hinges upon higher connectivity could render brain hubs more vulnerable to deficits in energy delivery or utilization and help explain their sensitivity to neurodegenerative conditions, such as Alzheimer’s disease.
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The ability to resist the urge to eat requires the proper functioning of neuronal circuits involved in top-down control to oppose the conditioned responses that predict reward from eating the food ...and the desire to eat the food. Imaging studies show that obese subjects might have impairments in dopaminergic pathways that regulate neuronal systems associated with reward sensitivity, conditioning and control. It is known that the neuropeptides that regulate energy balance (homeostatic processes) through the hypothalamus also modulate the activity of dopamine cells and their projections into regions involved in the rewarding processes underlying food intake. It is postulated that this could also be a mechanism by which overeating and the resultant resistance to homoeostatic signals impairs the function of circuits involved in reward sensitivity, conditioning and cognitive control.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Based on brain imaging findings, we present a model according to which addiction emerges as an imbalance in the information processing and integration among various brain circuits and functions. The ...dysfunctions reflect (a) decreased sensitivity of reward circuits, (b) enhanced sensitivity of memory circuits to conditioned expectations to drugs and drug cues, stress reactivity, and (c) negative mood, and a weakened control circuit. Although initial experimentation with a drug of abuse is largely a voluntary behavior, continued drug use can eventually impair neuronal circuits in the brain that are involved in free will, turning drug use into an automatic compulsive behavior. The ability of addictive drugs to co-opt neurotransmitter signals between neurons (including dopamine, glutamate, and GABA) modifies the function of different neuronal circuits, which begin to falter at different stages of an addiction trajectory. Upon exposure to the drug, drug cues or stress this results in unrestrained hyperactivation of the motivation/drive circuit that results in the compulsive drug intake that characterizes addiction.
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Dysfunctions in frontostriatal circuits have been associated with craving and cognitive control in smokers. However, the relevance of white matter (WM) diffusion properties of the ventral and dorsal ...frontostriatal tracts for behaviors associated with smoking remains relatively unknown, especially in young adulthood, a critical time period for the development and maintenance of addiction. Here, diffusion tensor imaging (DTI) and probabilistic tractography were used to investigate the WM tracts of the ventral and dorsal frontostriatal circuits in two independent studies (Study1: 36 male smokers (21.3 ± 1.3 years) vs. 35 male nonsmokers (21.2 ± 1.3 years); Study2: 29 male smokers (21.4 ± 1.1 years) vs. 25 male nonsmokers (21.0 ± 1.4 years)). Subjective craving was measured by the Questionnaire on Smoking Urges (QSU) and cognitive control ability was assessed with the Stroop task. In both studies, smokers committed more response errors than nonsmokers during the incongruent condition of the Stroop task. Relative to controls, smokers showed lower fractional anisotropy (FA) and higher radial diffusivity in left medial orbitofrontal cortex-to-nucleus accumbens fiber tracts (ventral frontostriatal path) and also lower FA in right dorsolateral prefrontal cortex-to-caudate fiber tracts (dorsal frontostriatal path). The FA values of the right dorsal fibers were negatively correlated with incongruent response Stroop errors in smokers, whereas the mean diffusivity values of the left ventral fibers were positively correlated with craving in smokers. Thus, WM diffusion properties of the dorsal and ventral frontostriatal tracts were associated with cognitive control and craving, respectively, in young male tobacco smokers. These data highlight the importance of studying WM in relation to neuropsychological changes underlying smoking.
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5.
Addiction: Beyond dopamine reward circuitry Volkow, Nora D; Wang, Gene-Jack; Fowler, Joanna S ...
Proceedings of the National Academy of Sciences,
09/2011, Volume:
108, Issue:
37
Journal Article
Peer reviewed
Open access
Dopamine (DA) is considered crucial for the rewarding effects of drugs of abuse, but its role in addiction is much less clear. This review focuses on studies that used PET to characterize the brain ...DA system in addicted subjects. These studies have corroborated in humans the relevance of drug-induced fast DA increases in striatum including nucleus accumbens (NAc) in their rewarding effects but have unexpectedly shown that in addicted subjects, drug-induced DA increases (as well as their subjective reinforcing effects) are markedly blunted compared with controls. In contrast, addicted subjects show significant DA increases in striatum in response to drug-conditioned cues that are associated with self-reports of drug craving and appear to be of a greater magnitude than the DA responses to the drug. We postulate that the discrepancy between the expectation for the drug effects (conditioned responses) and the blunted pharmacological effects maintains drug taking in an attempt to achieve the expected reward. Also, whether tested during early or protracted withdrawal, addicted subjects show lower levels of D2 receptors in striatum (including NAc), which are associated with decreases in baseline activity in frontal brain regions implicated in salience attribution (orbitofrontal cortex) and inhibitory control (anterior cingulate gyrus), whose disruption results in compulsivity and impulsivity. These results point to an imbalance between dopaminergic circuits that underlie reward and conditioning and those that underlie executive function (emotional control and decision making), which we postulate contributes to the compulsive drug use and loss of control in addiction.
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Cannabis Addiction and the Brain: a Review Zehra, Amna; Burns, Jamie; Liu, Christopher Kure ...
Journal of neuroimmune pharmacology,
12/2018, Volume:
13, Issue:
4
Journal Article
Peer reviewed
Open access
Cannabis is the most commonly used substance of abuse in the United States after alcohol and tobacco. With a recent increase in the rates of cannabis use disorder (CUD) and a decrease in the ...perceived risk of cannabis use, it is imperative to assess the addictive potential of cannabis. Here we evaluate cannabis use through the neurobiological model of addiction proposed by Koob and Volkow. The model proposes that repeated substance abuse drives neurobiological changes in the brain that can be separated into three distinct stages, each of which perpetuates the cycle of addiction. Here we review previous research on the acute and long-term effects of cannabis use on the brain and behavior, and find that the three-stage framework of addiction applies to CUD in a manner similar to other drugs of abuse, albeit with some slight differences. These findings highlight the urgent need to conduct research that elucidates specific neurobiological changes associated with CUD in humans.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The correspondence between cerebral glucose metabolism (indexing energy utilization) and synchronous fluctuations in blood oxygenation (indexing neuronal activity) is relevant for neuronal ...specialization and is affected by brain disorders. Here, we define novel measures of relative power (rPWR, extent of concurrent energy utilization and activity) and relative cost (rCST, extent that energy utilization exceeds activity), derived from FDG-PET and fMRI. We show that resting-state networks have distinct energetic signatures and that brain could be classified into major bilateral segments based on rPWR and rCST. While medial-visual and default-mode networks have the highest rPWR, frontoparietal networks have the highest rCST. rPWR and rCST estimates are generalizable to other indexes of energy supply and neuronal activity, and are sensitive to neurocognitive effects of acute and chronic alcohol exposure. rPWR and rCST are informative metrics for characterizing brain pathology and alternative energy use, and may provide new multimodal biomarkers of neuropsychiatric disorders.
Opioid receptors are expressed throughout the brain and play a major role in regulating striatal dopamine (DA) release. Clinical studies have shown that naloxone (NAL, a nonspecific opioid ...antagonist) in individuals with opioid use disorder and morphine (MRP, a nonspecific opioid agonist) in healthy controls, resulted in DA release in the dorsal and ventral striatum, respectively. It is not known whether the underlying patterns of striatal DA release are associated with the striatal distribution of opioid receptors. We leveraged previously published PET datasets (collected in independent cohorts) to study the brain‐wide distribution of opioid receptors and to compare striatal opioid receptor availability with striatal DA release patterns. We identified three major gray matter segments based on availability maps of DA and opioid receptors: striatum, and primary and secondary opioid segments with high and intermediate opioid receptor availability, respectively. Patterns of DA release induced by NAL and MRP were inversely associated and correlated with kappa (NAL: r(68) = −0.81, MRP: r(68) = 0.54), and mu (NAL: r(68) = −0.62, MRP: r(68) = 0.46) opioid receptor availability. Kappa opioid receptor availability accounted for a unique part of variance in NAL‐ and MRP‐DA release patterns (ΔR2 >0.14, p <.0001). In sum, distributions of opioid receptors distinguished major cortical and subcortical regions. Patterns of NAL‐ and MRP‐induced DA release had inverse associations with striatal opioid receptor availability. Our approach provides a pattern‐based characterization of drug‐induced DA targets and is relevant for modeling the role of opioid receptors in modulating striatal DA release.
We characterized the brain‐wide distribution of opioid receptors and, within the striatum, studied their association with drug‐induced dopamine release patterns. There was highest opioid receptor availability in a brain primary opioid segment including frontal, temporal, limbic, thalamic, cerebellar vermis, and periaqueductal gray regions. Patterns of dopamine release induced by naloxone and morphine were inversely related and were both associated with mu and uniquely with kappa opioid receptor availability. The data revealed major brain opioid segments and showed that striatal DA release patterns were related to the pharmacology of opioid drugs.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Emotion Recognition Biases in Alcohol Use Disorder Freeman, Clara R.; Wiers, Corinde E.; Sloan, Matthew E. ...
Alcoholism, clinical and experimental research,
August 2018, Volume:
42, Issue:
8
Journal Article
Peer reviewed
Background
Alcohol use disorder (AUD) has been associated with impairments in cognitive and emotional function, including difficulty identifying emotional facial expressions. However, it is unclear ...whether these deficits are associated with alcohol consumption or related anxious and depressive symptoms.
Methods
We compared the recognition of emotional faces expressing happiness, surprise, sadness, fear, anger, and disgust in 19 AUD participants and 19 healthy volunteers using the Cambridge Neuropsychological Test Automated Battery Emotion Recognition Task. We analyzed group differences in response latency, accuracy, and misidentification patterns (as defined by the tendency to mislabel facial expressions as exhibiting specific emotions). To assess whether misidentification patterns were associated with drinking severity, we also examined associations with alcohol consumption over the past 90 days.
Results
There were no differences in response latency or accuracy between groups. However, there were group differences in misidentification patterns. While controls tended to misidentify emotional expressions as happy, those with AUD tended to misidentify expressions as angry or disgusted. In AUD participants, the degree to which individuals were biased toward anger or disgust was positively correlated with the number of drinks they consumed in the past 90 days but was not associated with depression or anxiety scores.
Conclusions
Our findings suggest that individuals with AUD have a bias toward misidentifying emotional facial expressions as hostile, which is not mediated by associated mood changes. This provides further evidence of disrupted social cognition in AUD.
Individuals with alcohol use disorder were more likely to misidentify ambiguous emotional facial expressions as displaying anger and disgust as compared to healthy controls. In individuals with alcohol use disorder, these disgust and anger biases correlated positively with alcohol consumption over the past 90 days. Our results provide evidence of altered social cognition in individuals with alcohol use disorder.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Obese individuals exhibit brain alterations of resting-state functional connectivity (RSFC) integrity of resting-state networks (RSNs) related to food intake. Bariatric surgery is currently the most ...effective treatment for combating morbid obesity. How bariatric surgery influences neurocircuitry is mostly unknown. Functional connectivity density (FCD) mapping was employed to calculate local (lFCD)/global (gFCD) voxelwise connectivity metrics in 22 obese participants who underwent functional magnetic resonance imaging before and 1 month after sleeve gastrectomy (SG), and in 19 obese controls (Ctr) without surgery but tested twice (baseline and 1-month later). Two factor (group, time) repeated measures ANOVA was used to assess main and interaction effects in lFCD/gFCD; regions of interest were identified for subsequent seed to voxel connectivity analyses to assess resting-state functional connectivity and to examine association with weight loss. Bariatric surgery significantly decreased lFCD in VMPFC, posterior cingulate cortex (PCC)/precuneus, and dorsal anterior cingulate cortex (dACC)/dorsomedial prefrontal cortex (DMPFC) and decreased gFCD in VMPFC, right dorsolateral prefrontal cortex (DLPFC) and right insula (p
< .05). lFCD decreased in VMPFC and PCC/precuneus correlated with reduction in BMI after surgery. Seed to voxel connectivity analyses showed the VMPFC had stronger connectivity with left DLPFC and weaker connectivity with hippocampus/parahippocampus, and PCC/precuneus had stronger connectivity with right caudate and left DLPFC after surgery. Bariatric surgery significantly decreased FCD in regions involved in self-referential processing (VMPFC, DMPFC, dACC, and precuneus), and interoception (insula), and changes in VMPFC/precuneus were associated with reduction in BMI suggesting a role in improving control of eating behaviors following surgery.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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